Parrotfish Helping to Maintain a Healthy Reef

Photo and article by Hannah Rempel

Hannah Rempel and Robin Gropp from Lewis & Clark College in Portland, Oregon are working with the BNMP to conduct research on the stoplight and queen parrotfishes. Specifically, they are investigating parrotfish abundance and population structure, foraging rates, algae removal rates and the overall percent algae cover on the reef.

Why care about coral reefs? Aside from their natural beauty, coral reefs are among the most biologically diverse ecosystems on the planet. Scientists estimate that one quarter of all ocean species depend on coral reefs. Additionally, they are a critical source of food for millions of people, protect coastlines from the damaging effects of tropical storms, provide spawning and nursery grounds for millions of sea creatures, and are even a vital source of new medicines.

Coral reefs are in trouble. Over the past 50 years it is estimated that 33 to 50 % of our planet’s coral reefs have been degraded or lost. Unfortunately, most of the damage is due to human activities such as overfishing (particularly of herbivorous fish), destructive fishing methods (using dynamite or cyanide), unsustainable tourism (contact from divers or boat anchors), changing ocean chemistry, and pollution (litter, oil, discharge of sewage or wastewater).

The slippery slope to slime. Coral and certain types of algae compete for space on the reef. In recent decades, the amount of reef algae has increased dramatically – effectively smothering the corals by choking off oxygen and disrupting helpful bacteria. Scientists have dubbed this process “the slippery slope to slime.” Herbivorous fishes are critically important to maintaining healthy coral reefs because they graze on algae, thus preventing it from overgrowing corals. On Bonaire, one of the most important groups of herbivores is parrotfish. Without constant grazing from parrotfish, the algae grows tall and thick, overgrowing coral and in turn making it harder for fish to eat it. Between 2003 to 2009 the number of parrotfish on Bonaire dropped dramatically and there was a noticeable boom in algae growth. The main threats to parrotfish are overfishing, destruction of seagrass and mangroves where young parrotfish live, and pollution. The Bonaire National Marine Park (BNMP) created two Fish Protected Areas in 2008, and banned the harvest of parrotfish island-wide in 2010. Since then, parrotfish populations have increased, but the decline in resilience of Bonaire’s reefs remains a concern.

Knowledge is power. There is an increasing awareness of the need to understand the current state of coral reefs and to find effective ways to protect coral habitats. Many factors may be at play, but continued research is essential if we are to make effectual policy, and foster marine stewardship. Currently, Hannah Rempel and Robin Gropp from Lewis & Clark College in Portland, Oregon are working with the BNMP to conduct research on the stoplight and queen parrotfishes. Specifically, they are investigating parrotfish abundance and population structure, foraging rates, algae removal rates and the overall percent algae cover on the reef. They will compare this study to one conducted by the scientist Bruggeman and his colleagues in 1994 to see if and how parrotfish foraging behavior has changed in the past two decades. In addition, they are investigating how humans may be influencing parrotfish behavior by comparing a more remote site (Karpata) and an urban site (Yellow Submarine). Overall, this study will help us better understand how parrotfish help facilitate coral reef health.

We thank Dive Friends Bonaire for supporting this research and helping make this study possible. In the words of the DFB motto, ‘Without blue, there is no green’.